EP2956292B1 - Packaging of a group of at least two containers made of plastic material - Google Patents

Description

The present invention relates to a method of manufacturing containers, wherein a group of at least two plastic containers is provided, each container having a body and a rim.

It is known to pack plastic containers in groups of several containers. These are in particular containers containing a food product, such as yogurt, compote or the like. According to a first option, the containers are detached from each other, but they are grouped in one and the same package, for example a box or wrapping that keeps them relative to each other. In this case, to consume the contents of the containers, the user must extract them from the box or remove the wrapping. The packaging is relatively expensive, since it requires an external element (box or wrapping). On the other hand, the manipulations requested from the user are relatively demanding since, for example, once the wrapping removed, the containers are unbundled and can no longer be handled as a whole. In addition, the box or wrapping constitute waste.

To eliminate these disadvantages, it is known to manufacture containers bound together by their flanges.

Devices for connecting plastic containers by their flanges are known, for example, from patent documents FR 2 532 240 A1 , DE 199 21 033 A1 , and EP 0 050 083 A1 . With such devices, containers are connected together separately manufactured by thermoforming or injection.

Another possibility, illustrated for example in the patent document FR 2 449 604 A1 is to thermoform the containers from the same plastic sheet, their edges remaining substantially in the initial plane of the sheet. For example, as the document proposes FR 2 449 604 A1 the containers are made from the same sheet driven in step by being unwound from a reel. In another example, the containers are manufactured in groups, each group being made in a plastic sheet or wafer. The containers are optionally separated at the output of the production line.

In another example, the containers remain grouped, and, to facilitate the separation of the containers relative to each other, notches are made in the delimiting zones of these edges.

Economically, grouped containers are thus easily usable. On the other hand, the difficulty is to manage to break the lines of connection between the edges. This leads to the choice, for the thermoplastic material, of a material both thermoformable and easily scored. For this reason, such containers are generally made of polystyrene. However, polystyrene is relatively expensive and has some environmental harmfulness, if only because it is difficult to recycle. However, other materials having the properties required to form containers, for example able to contain food materials, do not necessarily have the ability to easily break when notched. This is for example the case of polypropylene.

For this reason, the invention aims to provide a method of forming, filling and sealing containers, wherein the containers can be grouped by being bonded together, while allowing easy rupture of this connection, even if the material is not easily breakable as is the case of polystyrene.

Thus, the invention relates to a method of forming, filling and sealing a group of at least two plastic containers, in which, from the same sheet of plastic material, containers are each thermoformed. a body and a rim which delimits an opening, the containers are filled, the containers are closed by placing lids across their openings, the containers are separated by cutting them individually in the sheet, and after having separated the containers, the containers of the adjacent group so that sections of their respective flanges are opposite and delimit between them a line of separation between the adjacent containers and is carried out, on the separation line, at least one weld forming a breakable connection between the sections of edges opposite.

Thus, compared with a conventional manufacturing process for thermoforming containers in material such as polystyrene, it is not enough to make notches between the edges of adjacent containers, but these edges are cut so as to completely separate the containers. from each other. Then, according to the method, one or more welding points are produced on lines of separation between the adjacent containers that are to be grouped.

With the invention, the choice is made to initially have the containers separated from each other while placing them so that sections of their edges are opposite and, in practice, touch-key, the distance between the edges next to it being practically nil. For example, the containers may be made by thermoforming in the same sheet of thermoplastic material, but be separated from each other by cutting in this sheet.

The invention makes the choice, starting from containers initially manufactured in groups and then separated, to make one or more points of welding between them. Of particular interest in the case of containers thermoformed in the same polypropylene sheet, the Applicant has found that such weld points are more easily scored than would be bonds preserved in the sheet after a simple partial cut in portions of edges of containers. For the purposes of the present description, the term "breakable" is used to describe the possibility of causing a breakage without tools and using a low manual force. The term "break" is in the same sense.

For the purposes of the present invention, the term "welding point" includes a very localized area, of short length compared to that of the edges of the edges.

According to one embodiment, the rim of each container defining an opening, the said at least one weld is made on the line of separation between the adjacent containers, from the faces of the rims of said containers which are opposite their openings.

To separate the containers having an opening, there is a tendency to tilt them relative to each other by bringing their respective apertures closer to one another. The Applicant has found that by producing the weld point from the face of the edges opposite to the opening, this welding point is subjected to maximized tensile forces during this tilting, so that the break is facilitated. In addition, the weld spot is little or not visible from the face where is the opening, which is usually the most visible face. In addition, if the openings of the containers are closed by a cover or a seal at the moment when the spot is made, the presence of this lid or cap does not interfere with the completion of the weld spot.

According to one embodiment, the weld point extends over only a portion of the thickness of the opposite edges.

This is done so that, when trying to separate two adjacent containers by tilting them towards each other, the edges of their respective flanges located at the weld point or points can serve as a support point forming a lever axis that facilitates the breaking of the weld point.

According to one embodiment, the welding point is made by local melting of the plastic material.

Thus, the welding is carried out without the addition of external material, and very simply and economically.

According to one embodiment, the plastics material comprises polypropylene.

Polypropylene has an economic and environmental advantage. Thanks to the invention, it is possible to produce polypropylene bundles, while allowing the separation of these containers by breaking the bond or points that bind them.

According to one embodiment, the lids are lids affixed to the openings of the containers from a continuous strip, and the lids are cut during the separation of the containers.

The invention also relates to an installation for forming, filling and sealing containers.

As indicated at the beginning of this text, it is known to group initially separated containers, putting them in a box or wrapping them in a streamer. According to another prior art, there is known the possibility of maintaining links between the edges of adjacent containers, delimiting these rims only by partial notches of the plastic material. Given the aforementioned drawbacks of this prior art, the invention aims to provide an installation that provides breakable connections between containers grouped simply and economically.

Thus, the facility for forming, filling and sealing containers according to the invention comprises a thermoforming station suitable for thermoforming, from a sheet of plastic material, containers each having a body and a rim defining an opening , as well as a conveyor for conveying thermoformed containers in groups of at least two adjacent containers bound by a portion of the sheet, a container filling station, a container closure station and a cutting station adapted to cut the containers individually in said sheet to separate them, and the installation comprises, in downstream of the container cutting station in the conveying direction of the containers, means for arranging the containers of the adjacent group, such that sections of their respective flanges are opposite and delimit between them a line of separation between the adjacent containers and the installation also comprises a welding tool capable of producing, on the separation line, at least one weld point forming a breakable connection between the opposite edges.

Thus, the installation of the invention makes it possible to achieve one or more points of welding between the flanges opposite the adjacent containers initially separated, to allow them to be connected in a breakable manner. The welding tool is integrated into a "Form-Fill-Seal" installation, which means forming, filling and closing the containers. It is only a simple job to set up, without significant additional cost.

According to one embodiment, the installation comprises at least one welding electrode and means for applying this electrode to the faces of the rims of the containers opposite their openings.

According to one embodiment, the installation of containers comprises at least two spaced apart welding electrodes.

According to one embodiment, the installation comprises means for holding the groups of separate containers such that, for each group, the flanges facing the containers are accessible by their opposite faces to the openings of the containers.

According to one embodiment, the lids are lids affixed to the openings of the containers from a continuous strip, and the cutting station is able to cut the lids during the separation of the containers.

• la figure 1 montre schématiquement une installation de fabrication de récipients, comprenant le dispositif de l'invention et permettant de mettre en oeuvre le procédé de l'invention ;
• la figure 2 montre deux récipients groupés, lors de la réalisation d'un point de soudure sur les lignes de séparation entre ces récipients ;
• la figure 3 est une vue de dessus d'un groupe de quatre récipients obtenu conformément à l'invention ;
• la figure 4 est un agrandissement montrant des points de soudure entre les rebords en regard de deux récipients ;
• la figure 5A est une vue de dessous d'une partie du dispositif de conditionnement ;
• la figure 5B est une vue en coupe selon la ligne VB-VB de la figure 5A ;
• la figure 6 montre en détail la zone de la jonction entre des rebords de deux récipients adjacents réalisée par un point de soudure selon l'invention, dans la situation de transport ou de stockage de ces récipients ; et
• la figure 7 est une vue correspondant à celle de la figure 6, au moment où l'on sépare deux récipients adjacents.

The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of an embodiment shown by way of non-limiting example. The description refers to the accompanying drawings in which:

• the figure 1 shows schematically a container manufacturing installation, comprising the device of the invention and for implementing the method of the invention;
• the figure 2 shows two grouped containers, when performing a weld spot on the lines of separation between these containers;
• the figure 3 is a top view of a group of four containers obtained according to the invention;
• the figure 4 is an enlargement showing weld points between the edges facing two containers;
• the Figure 5A is a bottom view of a portion of the conditioning device;
• the Figure 5B is a sectional view along line VB-VB of the Figure 5A ;
• the figure 6 shows in detail the area of the junction between flanges of two adjacent containers made by a weld spot according to the invention, in the situation of transport or storage of these containers; and
• the figure 7 is a view corresponding to that of the figure 6 at the moment when two adjacent containers are separated.

First of all, the container manufacturing plant is shown schematically on the figure 1 . This installation comprises, arranged successively in the direction F of a strip 10 of thermoplastic material unwound from a coil 12, a heating station 14 in which the thermoplastic material is brought to a temperature allowing its plastic deformation, a thermoforming station 16 in which, from the thermoplastic strip 10, the containers 18 are thermoformed, a filling station 20 of the containers, a station 22 for closing the containers, a station 24 for cutting the containers and a packaging device 26.

In the example shown, the containers are thermoformed from a continuous strip. In the context of the present description, it will generally be considered that the containers are thermoformed from a sheet of thermoplastic material. This sheet may take the form of a continuous strip as shown in FIG. figure 1 or a wafer in which the containers are thermoformed individually or in groups. Of course, if the containers are individually thermoformed, the cutting station 24 is not always necessary except possibly to cut the closing caps of the containers if, as in the example of the figure 1 these lids are affixed to the openings of the containers from a continuous strip 23.

The containers are particularly suitable for containing a food product, such as yogurt, compote or the like. Thus, the filling station 20 injects such a product into the containers, in the desired proportions.

Although the figure 1 shows, in the station 22, the closure of the containers from a web 23 continues, one could of course provide other types of closure stations, for example stations affixing individual covers across the openings of the section.

The cutting station 24 comprises, in a conventional manner, knives 24A and a cutting counter-tool 24B which cooperates with the face of the rims of the containers which is opposite to the knives 24A. Indeed, as we see better on Figures 2 and 3 , the containers 18 comprise a body 17 and a flange 19. In general, the flange is located in the plane of the sheet in which the containers are thermoformed, the material being substantially not stretched in this area during thermoforming.

At the outlet of the cutting station 24, the containers are conveyed to the packaging device 26 by a conveyor 28 capable of conveying them individually. For example, a "pilgrim-type" conveyor is used. Conventionally, such a conveyor comprises, on the one hand, support means for the containers and, on the other hand, transport means, which grip the containers and drive them in a step to refit them on supports arranged in a downstream region.

For example, on the figure 2 , there are shown transport pads 30 on which bases 17B can rest containers opposed to their openings 17A. In the case in point, these studs have heels 30A which rise slightly against the upstream side walls of the containers so that, while advancing in the direction F downstream, the studs cause the containers they carry. In this example, the media are formed by rails 32 parallel to the direction of travel F, on which the edges of the containers rest. The central rail 32 to be traversed by electrodes 34 so that they can approach the edges of the containers and perform their welding function, this rail has holes 33 through which pass these electrodes 34.

When, as in the example of figure 1 , the containers are thermoformed from a continuous strip, the installation may comprise a first type of gripper conveyor or the like advancing step by step, to advance the strip 10 as a whole and, from the exit of the post cutter 24, a conveyor of the conveyor type 28, capable of transporting individual containers, preferably keeping them grouped together. In this respect, the pilgrim conveyor is an example of a possible conveyor. To simplify the drawing, the first conveyor is not represented on the figure 1 .

On the figure 2 it is understood that in the packaging device 26, the containers 18 grouped are arranged such that sections of their respective flanges 19 are located opposite by delimiting between them a dividing line. This provision is also clearly visible on the figure 3 , for a group of four containers, 18A to 18D. It can be seen that the sections 19'A of the rim 19 of the container 18A are opposite, respectively, with a section 19'B of the rim of the container 18B and a section 19'D of the rim of the container 18D. Another section 19'B of the rim of the container 18B is opposite a portion 19'C of the rim of the container 18C, another section 19'C is opposite another section 19'D of the rim of the container 18D . The different sections facing each other are disposed edge-to-edge, touching or very close to touching each other, that is to say that the width of the line of separation 19 'between two flange sections facing extremely low, or practically negligible.

While the containers are thus maintained, according to the invention, the welding points are made to connect two containers with the edges of the sections are opposite. In the example shown on the figure 3 for each line of separation between two flange sections facing each other, three weld points 36 were produced. Of course, a different number of weld points could be provided. It is however interesting to have at least two solder points spaced along the line of separation.

For the purposes of the present invention, a "weld spot" designates a very localized zone in which, by means of a weld, a bridge is established between the flanges opposite two receptacles. The length l (see figure 4 ) of these weld points measured in the direction of the separation line is small. It is generally between 1 mm and 12 mm, preferably between 2 and 7 mm, more preferably between 3 and 5 mm. The area of the areas constituting the weld points corresponds to the surface of the head 34A of the welding electrodes. It has for example a circular outline, oval or square or rectangular. The length l indicated above can therefore be the diameter of a weld zone, or its transverse or longitudinal dimension. The surface of the weld zone may advantageously be less than 150 mm ² , preferably of the order of 10 to 50 mm ² .

With reference to the figure 2 it will be recalled that, in the example shown, the conveyor 28 comprises, on the one hand, transport pads 30 and, on the other hand, supports 32 for the containers. We see on the figure 2 that the device also comprises a holding plate 38 which cooperates with the containers on the opposite side to the pads 30. Thus, when the containers are kept grouped to be interconnected in the packaging device, they are sandwiched between the pads 30 and the retaining plate 38. At this stage, the electrodes, which pass through the supports 32 if necessary, get closer to the rims of the containers to achieve the soldering points. In the example shown, the weld points are effect on the lines of separation 19 'between the containers from the lower faces of the flanges 19, that is to say from the faces of these flanges which are opposite the 17A openings of the containers, themselves covered by the covers 18A.

On the Figure 5A , there is shown the holding plate 38 in a view from below. Its lower surface is adapted to cooperate with the upper faces of the containers, at least in the region of the edges of the latter, to not only maintain the containers but also form a counter-tool for the welding electrodes 34.

In addition, the lower face of the plate 38 may be arranged to center and wedge laterally the containers of the same group. For this purpose, this plate 38 has several centering members. It is on the one hand a centering core 38A which protrudes under the lower face of the plate 38 to cooperate with the free zone Z between the edges of the four adjacent containers visible on the figure 3 . It is on the other hand of centering ramps 38B which are arranged in the corners of the plate 38 and centering ramps 38C which are arranged on the sides of this plate, to cooperate with corners of the edges of the containers, located on the outer contour of the group of containers. On the cut of the Figure 5B it will be seen that the centering cores 38A and the centering ramps 38B and 38C have shapes that become thinner as one moves away from the underside of the plate 38 to facilitate centering. If several adjacent plates 38 are considered together, their adjacent centering ramps 38B or 38C together form a centering core of a shape similar to that of core 38A.

On the Figure 5A the positions of the soldering electrodes 34 and the arrangement of the transport pads 30 and the supports 32 are also seen. The transport pads 30 are driven by any appropriate means, for example by being carried by jacks allowing their vertical displacements and horizontal. The pads are mounted to come carry containers and slightly away from the supports 32, move horizontally to bring these containers to the next step, then go down to rest these containers on the supports and return to the initial position, under other containers.

The choice of a group of four containers is only one example, which is why the present text refers, in general, to a group of at least two containers. Furthermore, conventionally, a row of containers transverse to the direction of advance F comprises more than two containers, for example eight containers. Thus, even for groups of four containers, a holding plate 38 can cover two containers in the direction F and cover the entire row in the transverse direction.

On the figure 6 the region of a weld point is seen between the respective flanges 19 of these containers. It can be seen that the weld point 36 extends only over part of the thickness E of the flanges 19. Thus, the thickness e of the weld point 36 can be of the order of 2 to 4/10 ^th of millimeters, for a thickness E of the order of 1 mm. On the figure 6 for better understanding, the width ls of the line of separation 19 'is intentionally exaggerated. This difference in thickness can be obtained by appropriately choosing the temperature at which the electrodes carry the material and the duration of exposure to this temperature.

As has been indicated, the welding points are advantageously made by the electrodes. Thus, the welding is advantageously carried out by local melting of the plastic material, without the addition of external material. By the way, on the figure 6 traces of creep of the material due to this local fusion are seen.

On the figure 7 the two containers 18 are being separated. For this, they are folded towards each other along the line of separation 19 '. This folding is done naturally in the direction by bringing closer to each other the respective lids 18A of these containers 18. During this movement, the weld point 36 is subjected to very large tensile stresses, all the more so. that the edges of the sections of the opposite edges can touch, which can produce a leverage effect. Under the effect of these tensile stresses, being reminded that the thickness of the weld points is small and their overall dimensions are small, the material constituting these weld points breaks, so that the containers can be separated.

The plastic in which the containers are thermoformed is preferably polypropylene, this material provides good protection for the contents of the containers (it provides a water vapor barrier greater than that of polystyrene) and can be recycled easily. In addition, the cost of polypropylene is lower than that of polystyrene. However, unlike polystyrene, polypropylene does not tend to break under the effect of folding. Thanks to the invention, by producing localized welding points as described, it is however possible to produce grouped containers with, between them, breakable connections for their individual use. Indeed, the weld points being added on initially separate containers, the forces involved are not only bending forces, but also tensile forces, which allow the expected break.

Claims (12)

1. A method of forming, filling, and sealing a group of at least two containers (18) made of plastics material, which method consists in: thermoforming containers from the same sheet of plastics material (10), each of which containers has a body (17) and a rim (19) that defines an opening (17A); filling the containers; closing the containers by placing lids (18A) across their openings; and separating the containers (18) by cutting them out individually from the sheet;
   said method being characterized in that, after the containers have been separated, the method further consists in: placing the containers (18) adjacent to one another in such a manner that segments of their respective rims (19) face each other and define between them a line of separation (19') between the adjacent containers; and, on the line of separation, forming at least one spot weld (36) forming a breakable connection between the facing rim segments.
2. A method according to claim 1, characterized in that, with the rim (19) of each container (18) defining an opening (17A), said at least one spot weld (36) is formed on the line of separation (19') between the adjacent containers, from those faces of the rims of said containers that face in the direction that is opposite from the direction in which their openings face.
3. A method according to claim 1, characterized in that at least two spot welds (36) are formed in spaced-apart manner on the line of separation.
4. A method according to of claim 1, characterized in that the spot weld (36) extends over only a fraction of the thickness (E) of the facing rims (19).
5. A method according to claim 1, characterized in that the spot weld (36) is formed by locally melting the plastics material.
6. A method according to claim 1, characterized in that the plastics material comprises polypropylene.
7. A method according to any one of claims 1 to 6, characterized in that the lids (18A) are membrane seals placed over the openings (17A) of the containers (18) in a continuous strip (23), and in that the seals (18A) are cut out while the containers are being separated.
8. An installation for forming, filling, and sealing containers, which installation comprises a thermoforming station (16) suitable for thermoforming containers (18) from a sheet of plastics material (10), each of which containers has a body (17) and a rim (19) that defines an opening (17A), as well as a conveyor for conveying the thermoformed containers in groups of at least two adjacent containers connected together via a portion of the sheet, a filling station (20) for filling the containers, a sealing station (22) for closing the containers with lids (18A) and a cutting station (24) suitable for cutting out the containers individually from said sheet so as to separate them,
   said installation being characterized in that, downstream from the container cutting station in the direction in which the containers are conveyed, it further comprises means (28) for placing the adjacent containers of the group in such a manner that segments of their respective rims (19) face each other and define between them a line of separation (19') between the adjacent containers, and in that it further comprises a welding tool (34) suitable for forming at least one spot weld (36) forming a breakable connection between the facing rims on the line of separation (19').
9. An installation according to claim 8, characterized in that it has at least one welding electrode (34) and means for applying said electrode against those faces of the rims (19) of the containers that face in the direction opposite from the direction in which their openings (17A) face.
10. An installation according to claim 9, characterized in that it has at least two welding electrodes (34) that are spaced apart.
11. An installation according to any one of claims 8 to 10, characterized in that it has means (32, 38) for maintaining the groups of containers separate in such a manner that, for each group, the facing rims (19) of the containers (18) are accessible via their faces that face in the direction opposite from the direction in which the openings (17A) of the containers face.
12. An installation according to any one of claims 8 to 10, characterized in that the lids (18A) are membrane seals placed over the openings (17A) of the containers (18) in a continuous strip (23), and in that the cutting station (24) is suitable for cutting out the seals while the containers are being separated.

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